Lithographic apparatus and device manufacturing method

Abstract

A position measurement system configured to measure a position quantity of a movable object in a measurement direction, the system including a radiation source, a beam splitter to split the radiation beam in a measurement beam and a reference beam, a first reflective surface mounted on the movable object to receive the measurement beam, a second reflective surface mounted on a reference object to receive the reference beam, and a detector arranged to receive a first and second reflected beam reflected by the first and second reflective surface, respectively, and configured to provide a signal representative of the position quantity of the movable object based on the first and the second beam, wherein the radiation source and detector are mounted on an object that is different from the movable object and the reference object.

What is claimed is: 
     
       1. A position measurement system configured to measure a position quantity of a movable object in a measurement direction, the position measurement system comprising:
 a radiation source configured to emit a single radiation beam; 
 a beam splitter configured to split the single radiation beam into a measurement beam and a reference beam; 
 a first reflective surface mounted on the movable object and configured to receive the measurement beam; 
 a second reflective surface mounted on a reference object and configured to receive the reference beam; and 
 a detector arranged to receive a first reflected beam reflected by the first reflective surface and a second reflected beam reflected by the second reflective surface, the detector configured to provide a signal representative of the position quantity of the movable object on the basis of the first and the second reflected beam, 
 wherein the radiation source and the detector are mounted on another object that is different from the movable object and the reference object, and 
 wherein the other object is a balance mass of a stage system. 
 
     
     
       2. The position measurement system of  claim 1 , wherein the beam splitter is spaced from the radiation source and the detector, and arranged closer to the movable object and/or reference object than the radiation source and the detector. 
     
     
       3. The position measurement system of  claim 1 , wherein the beam splitter is arranged on the reference object. 
     
     
       4. The position measurement system of  claim 1 , wherein the position measurement system comprises a retroreflector arranged to receive the first reflected beam reflected by the first reflective surface to reflect the first reflected beam back to the first reflective surface before the first reflected beam is received by the detector, and/or arranged to receive the second reflected beam reflected by the second reflective surface to reflect the second reflected beam back to the second reflective surface before the second reflected beam is received by the detector. 
     
     
       5. The position measurement system of  claim 1 , wherein the beam splitter is arranged on an intermediate object arranged between the movable object and the reference object. 
     
     
       6. The position measurement system of  claim 1 , wherein an intermediate object is arranged between the movable object and the reference object, and wherein a first and a second intermediate reflective surface are arranged on the intermediate object, each intermediate reflective surface being arranged at an angle of about 45 degrees with the measurement direction, wherein the first intermediate reflective surface is arranged to guide the measurement beam to the movable object, and the second intermediate reflective surface is arranged to guide the reference beam to the reference object. 
     
     
       7. The position measurement system of  claim 1 , wherein the position quantity of the movable object with respect to the reference object is determined based on intensity changes in a combination of the first reflected beam and the second reflected beam. 
     
     
       8. The position measurement system of  claim 1 , wherein the position measurement system is configured to determine a position quantity of the movable object with respect to the reference object or with respect to a second movable or stationary object. 
     
     
       9. The positioning measurement system of  claim 1 , wherein the second reflective surface and first reflective surface are part of the same movable object. 
     
     
       10. The position measurement system of  claim 1 , wherein at least one of the first and the second reflective surface is curved, wherein the detector comprises an array of CCDs, and wherein the position quantity of the movable object with respect to the reference object is determined based on fringe analysis of an image captured by the array of CCDs. 
     
     
       11. The position measurement system of  claim 1 , wherein at least one of the first and second reflective surface is curved, wherein the detector comprises an array of CCDs, and wherein light-dark patterns captured by the array of CCDs are used for a multiple degree of freedom position information of the movable object. 
     
     
       12. The position measurement system according to  claim 10 , wherein the measurement system is configured to detect surface and/or shape irregularities. 
     
     
       13. The position measurement system according to  claim 12 , wherein the surface and/or shape irregularities have static, quasi-static and/or dynamic behavior. 
     
     
       14. A lithographic apparatus comprising:
 a support constructed to support a patterning device, the patterning device being capable of imparting a beam of radiation with a pattern in its cross-section to form a patterned beam of radiation; 
 a substrate table constructed to hold a substrate; 
 a projection system configured to project the patterned beam of radiation onto a target portion of the substrate; and 
 a position measurement system configured to measure a position quantity of a movable object in a measurement direction, the position measurement system comprising
 a radiation source configured to emit a single radiation beam, 
 a beam splitter configured to split the single radiation beam in a measurement beam and a reference beam, 
 a first reflective surface mounted on the movable object configured to receive the measurement beam, 
 a second reflective surface mounted on a reference object configured to receive the reference beam, and 
 a detector arranged to receive a first reflected beam reflected by the first reflective surface and a second reflected beam reflected by the second reflective surface, the detector configured to provide a signal representative of the position quantity of the movable object on the basis of the first and the second beam, 
 
 wherein the radiation source and the detector are mounted on an object that is different from the movable object and the reference object, and 
 wherein the object is a balance mass of a stage system of the support or substrate table. 
 
     
     
       15. The lithographic apparatus of  claim 14 , wherein the movable object is the support or the substrate table, and wherein the reference object is the projection system. 
     
     
       16. The lithographic apparatus of  claim 14 , wherein an intermediate object is arranged between the movable object and the reference object, and wherein a first and a second intermediate reflective surface are arranged on the intermediate object, each intermediate reflective surface being arranged at an angle of about 45 degrees with the measurement direction, wherein the first intermediate reflective surface is arranged to guide the measurement beam to the movable object, and the second intermediate reflective surface is arranged to guide the reference beam to the reference object, the intermediate object being the support or the substrate table. 
     
     
       17. The lithographic apparatus of  claim 14 , wherein the position measurement system is configured to determine a position quantity of the movable object with respect to the reference object or with respect to a second movable or a stationary object. 
     
     
       18. A lithographic apparatus comprising:
 a support constructed to support a patterning device, the patterning device being capable of imparting a beam of radiation with a pattern in its cross-section to form a patterned beam of radiation; 
 a substrate table constructed to hold a substrate; 
 a projection system configured to project the patterned beam of radiation onto a target portion of the substrate; 
 a position measurement system configured to measure a position quantity of a movable object in a measurement direction, the position measurement system comprising
 a radiation source to emit a single radiation beam, 
 a first reflective and/or diffractive surface mounted on the movable object configured to receive a measurement beam generated by said single radiation beam, 
 a second reflective and/or diffractive surface mounted on a reference object configured to receive a reference beam generated by said single radiation beam, and 
 a detector arranged to receive a first beam from the first reflective and/or diffractive surface and a second beam from the second reflective and/or diffractive surface, the detector configured to provide a signal representative of the position quantity of the movable object on the basis of the first and the second beam, 
 
 wherein the radiation source and the detector are arranged on a balance mass of a stage system of the support or substrate table.